It has long been the common practice to use laborers to load and unload trucks. For heavy loads, mechanical devices such as cranes have long been used.
Due to the high cost and low efficiency of manual labor, several inventors have made efforts to provide self-loading trucks. Typically, self-loading trucks include vertical lifting chains to lift items from the ground or from a loading dock, and horizontal chains that carry the lifted objects onto the truck.
For example, Leroux U.S. Pat. No. 4,642,018 discloses a vertical lifting chain and a horizontal trolley chain for automatically loading a transport truck by means of suitable control means and motors that are built into the truck body.
Other U.S. Pat. Nos. showing self-loading trucks are 2,442,549 to Pearlman, 2,873,869 to Neaverson, 3,109,544 to Learmont and 2,211,721 to Gerosa. Moreover, German patent 1121550 also shows a structure of interest.